1. Field of the Invention
The present invention relates to motors generally and, more particularly, but not by way of limitation, to a novel linear actuator having a captivated lead screw and bearing pre-load adjustment.
2. Background Art
A linear actuator is a device used to perform operation along a linear path. One possible configuration of a linear actuator is one in which rotary motion is translated into linear motion by passing a lead screw through the threaded rotor of a rotary electric motor. In doing so, it is necessary to provide means to prevent rotation of the lead screw. This can be achieved using either external constraints or constraints internal to the actuator through captivation. The latter requires no external anti-rotation techniques.
Captive linear actuators provide anti-rotation by fastening anti-rotation shafts to the lead screw and passing this shaft through a bearing. The bearing is typically constrained with a sleeve mounted to a motor face. The shaft and bearing can be any configuration that allows linear translation without rotation of the shaft. Examples of this are splined, hexagonal, or butterfly shafts, etc. In motor applications using ball bearings for rotor rotation efficiency, it is necessary to pre-load the ball bearing between the inner and outer bearing race.
Accordingly, it is a principal object of the present invention to provide a linear motor with an internally captivated lead screw.
It is a further object of the invention to provide such a linear motor in which the pre-load of the ball bearings thereof is adjustable.
It is another object of the invention to provide such a linear motor that is economically constructed.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.
The present invention achieves the above objects, among others, by providing, in a preferred embodiment, a linear actuator, comprising: front and rear end bells; a stator structure; a rotor structure having first and second bearings journaled, respectively, in cavities formed in inner surfaces of said front and rear end bells; a captivation sleeve having its proximal end threadedly inserted in a cavity formed in an outer surface of said front end bell; and all foregoing elements being coaxially aligned to permit the insertion therethrough of a lead screw.